【Linux】Linux文件I/O

#define _GNU_SOURCE#include <stdio.h>#include <string.h>#include <stdlib.h>#include <errno.h>#include <unistd.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#define TOTAL 10//直接IO要考虑到硬件特性//磁盘最基本的单位是扇区，一个扇区512字节#define BUF_LEN 512int writeToFile(int fd,const char* buf,int len) {int wlen = 0;if ((wlen = write(fd, buf, len)) < 0) {fprintf(stderr,"write to %d failed,reason:%s.\n",fd,strerror(errno));return -3;}return wlen;}int main(int argc, char** argv) {//const char* TEXT = "This is a test.\n";char* buf = NULL;//buf = (char*)malloc(BUF_LEN); //地址要是512的倍数——内存边界对齐posix_memalign((void**)&buf,512,BUF_LEN);strcpy(buf,"This is test.\n");const char* filename = "./io_test.txt";int fd = 0;int i = 0;fd = open(filename,O_RDWR | O_TRUNC | O_CREAT | O_DIRECT);if (fd < 0) {fprintf(stderr, "fopen %s failed,reason:%s.\n exit\n",filename,strerror(errno));return -1;}for (i = 0; i < TOTAL; i++) {if (writeToFile(fd, buf, BUF_LEN) < 0) {fprintf(stderr,"write to %s failed,reason: %s.\n exit\n",filename,strerror(errno));//return -2;}printf("%d\n",i+1);}printf("finished.\n");//printf("Start to sleep 30 second....\n");if (buf)free(buf);close(fd);return 0;}

#define _GNU_SOURCE#include <stdio.h>#include <string.h>#include <stdlib.h>#include <errno.h>#include <unistd.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#define BUF_SIZE 512int main(int argc, char** argv) {char* buf = NULL;const char* filename = "./open_compare.txt";int fd = -1;time_t start;time_t cur;int rlen = 0;int ret = 0;static int read_total = 0;ret = posix_memalign((void**)&buf,512,BUF_SIZE);if (ret)fprintf(stderr,"posix_memalign failed.reason:%s\n",strerror(errno));start = time(NULL);do {read_total++;//fd = open(filename, O_RDWR | O_DIRECT);fd = open(filename,O_RDWR);if (fd < 0) { fprintf(stderr, "fopen %s failed,reason:%s.\n exit\n", filename, strerror(errno));return -1;}do {if ((rlen = read(fd, buf, BUF_SIZE)) < 0) {fprintf(stderr, "read to %s failed,reason: %s.\n exit\n", filename, strerror(errno));}} while (rlen>0);close(fd);cur = time(NULL);} while ((cur-start) < 20);printf("total time:%d\n",read_total);return 0;}

#include<unistd.h>int fsync(int fd);int fdatasync(int fd);void sync(void);